It's kind of hard to get too worked up over the treatment of animals we eat, but I can see this problem from a pragmatic perspective: animals kept in such conditions are far less healthy, obviously, and therefore far more inferior in quality than animals kept in free-range conditions and fed on their natural foods.
Simply put, a chicken kept in an open environment and allowed its natural diet is a far better meat animal than an undernourished one cooped up in a cage and wallowing in its own filth. According to this web site
, "[c]hickens are omnivores". They eat grass, other edible plants, and insects they dig up from the ground.
I think if we're going to be discussing the ethical treatment of meat animals, and convince others, we need to approach it from this angle. The costs of factory farming as opposed to small, family-owned farms that use natural fertilizers, feed and pesticides should be discussed from an economic basis. I think it's worth trying.